Earthquakes in Turkey

North-western Turkey, the county's most densely
populated region and industrial heartland, has
been struck by two massive earthquakes in 1999. The first,
on 17 August 1999 at 03:02 local, measured 7.4 on the Richter scale and
lasted 45 seconds. Izmit, an industrial city
of one million in western Turkey, was
nearest the epicenter. The official death toll stands at over 17,480, with
some 44,000 people injured, nearly 300,000 homes either damaged or collapsed
and more than 40,000 business premises similarly affected. On the day of
the catastrophe, the Turkish government declared a state of emergency and
requested international assistance.

The disaster was followed by more than 1,300 aftershocks, culminating
in the second quake - which shook Düzce and Kaynasli in the north-western province of Bolu, some 100 kilometers (63 miles) to the east of Izmit for 30 seconds
- at 18:57 on 12 November 1999 and rated 7.2 on the Richter scale. The
jolt was felt both in Istanbul (some 260 km
to the west) and Ankara, the nation's capital,
300 km to the east.

Izmit - Golcuk Quake (17 August 1999)

The Izmit earthquake occurred at 03:02 local time, and was centered at 40.702° N., 29.987°
E., which places the epicenter about 11 kilometers, or seven miles, southeast
of the city of Izmit. This location indicates
that the earthquake occurred on the northernmost strand of the North Anatolian
fault system. The earthquake originated at a depth of 17 kilometers, or
about 10.5 miles, and caused right-lateral strike-slip movement on the
fault. Preliminary field reports confirm this type of motion on the fault,
and initial field observations indicate that the earthquake produced at
least 60 kilometers (37 miles) of surface rupture and right-lateral offsets
as large as 2.7 meters, or almost nine feet.

The earthquake likely occurred on a branch of the North Anatolian
fault. Although this is the largest earthquake in the epicenter region
in this century, the region of the earthquake has a long history of destructive
earthquakes. In 1967, a magnitude 7.1 earthquake caused extensive damage
along the North Anatolian fault just east of
the current shock.

The 900 km-long North Anatolian fault has
many characteristics similar to California's San Andreas fault. These two
faults are right-lateral, strike-slip faults having similar lengths and
similar long-term rates of movement. If a person is looking across a right-lateral,
strike-slip fault during such an earthquake, that person would see the
opposite side move to the right.

The North Anatolian fault has produced seven
large (MS) 7.0 earthquakes in the period from 1939 through 1999. These
earthquakes have ruptured the fault progressively from east to west.

Earthquakes on the North Anatolian fault
are caused by the northwards motion of the Arabian plate against the Eurasian
plate, squeezing the small Turkish micro plate westwards. Also, compression
in this region is due to the northwards motion of the African plate, which
produces subduction at the Cyprus and Hellenic arcs. The small Turkish
micro plate is bounded on the east by the East Anatolian
fault zone (EAFZ), on the north by the North Anatolian
fault zone (NAFZ), on the west by a diffuse zone of deformation surrounding
the greater Aegean region, and on the south
by the Hellenic and Cyprus arcs.

Düzce Quake (12 November 1999)

A major earthquake occurred 70 kilometers (45 miles) east of Adapazari
or 170 km (105 mi) northwest of Ankara, Turkey
at 18:57 local time on November 12th, 1999. A magnitude of 7.2 was computed for this earthquake. This earthquake is
located about 110 km (70 miles) east of the magnitude 7.4 main shock on
August 17 which killed over 17,000 people and injured another 50,000 around
Izmit.

Casualty figures from this last earthquake stand around 845 confirmed dead and around 5,000 injured. The destruction in Bolu and Düzce was widespread, with the total affected population between 150,000 and 180,000. Some assessments indicated that over 18 thousand buildings have been heavily damaged and the Government has estimated the financial cost of the quake at 10 billion US dollars. Industrial facilities in the area have stopped their production due to power shortages and some have suffered major material damage.

During the morning of 17 November (Wednesday) two major aftershocks
(4.9 at 02h00 and 5.0 at 10h10) were felt in the provincial capital of
Bolu bringing more fear and despair to the population
as damaged buildings collapsed. About 24,000 families (80%
of the town's population) were homeless. The local crisis centre in Bolu
called upon rescue and humanitarian workers in Düzce for help in the
middle of the night. The Prime Minister's Crisis
Centre (PMCC) urgently sent 10,000 tents for the affected area.
Temporary houses were constructed as well.

Besides Bolu and Düzce, the neighboring
districts of Kaynasli (70% of the town is considered to be destroyed),
Akcakoca, Cumayeri, Gümüsova, Yigilca and Gölkaya have been
affected. With night-time temperatures dropping as low as minus two degrees
Celsius, the majority of the region's population remained outdoors either
because their homes were damaged or for fear of entering buildings even
though many appeared structurally sound. Population movements away from the
region were also increasing on a daily basis. According to the PMCC, 1,000
prefabricated houses constructed in Düzce for victims of the August
earthquake were been immediately reassigned to the locality.

Meanwhile, many hospital facilities in the affected area were damaged
and were no longer functioning. Field facilities surrounding the
hospital
buildings were set up immediately after the quake, with volunteer doctors
and nurses coming from nearby towns to treat the injured. Severe cases
were referred to hospitals both in Ankara
and Istanbul. All schools in Düzce and Kaynasli were closed due to damage and they continued to teach in winterized tents or temporary buildings.

Government crisis centers established in Düzce and
Bolu, coordinating search and rescue teams from all over the world. Some 12,000 rescue workers came to the area and the total number
of people pulled alive from collapsed buildings is estimated at 300. Rescue activities were ceased after some period giving way to the process of debris removal.

Van - Ercis Quake

Latest major earthquake hit Eastern Turkey, the province of Van and its district Ercis, on 23rd of October 2011, at 13:41 local time. A magnitude of 7.2 was computed for this earthquake and lasted less than 30 seconds. Hundreds of aftershocks were recorded, some being as large as 5,7 in magnitude causing some more damage.

Many buldings have collapsed during the earthquake in the city center and in Ercis town, as well as in its villages. The death toll has reached 644 people with over two thousand injured. Several rescue teams have immediately arrived on the spot to carry out their mission, a total of 222 residents were pulled out alive off the debris. Temporary tents and other equipments have been sent to the area. The officials are trying to replace tents with hard containers as soon as possible in order to ease the winter conditions, and then new homes will be constructed within a year or so.

For a list of earthquakes that caused more than 10,000 deaths in Turkey, please Click Here.

The Richter Magnitude Scale

Seismic waves are the vibrations from earthquakes that travel through the
Earth; they are recorded on instruments called seismographs. Seismographs
record a zigzag trace that shows the varying amplitude of ground oscillations
beneath the instrument. Sensitive seismographs, which greatly magnify these
ground motions, can detect strong earthquakes from sources anywhere in
the world. The time, locations, and magnitude of an earthquake can be determined
from the data recorded by seismograph stations.

The Richter magnitude scale was developed in 1935 by Charles F. Richter
of the California Institute of Technology as a mathematical device to compare
the size of earthquakes. The magnitude of an earthquake is determined from
the logarithm of the amplitude of waves recorded by seismographs. Adjustments
are included for the variation in the distance between the various seismographs
and the epicenter of the earthquakes. On the Richter Scale, magnitude is
expressed in whole numbers and decimal fractions. For example, a magnitude
5.3 might be computed for a moderate earthquake, and a strong earthquake
might be rated as magnitude 6.3. Because of the logarithmic basis of the
scale, each whole number increase in magnitude represents a tenfold increase
in measured amplitude; as an estimate of energy, each whole number step
in the magnitude scale corresponds to the release of about 31 times more
energy than the amount associated with the preceding whole number value.

At first, the Richter Scale could be applied only to the records from
instruments of identical manufacture. Now, instruments are carefully calibrated
with respect to each other. Thus, magnitude can be computed from the record
of any calibrated seismograph.

Earthquakes with magnitude of about 2.0 or less are usually call micro earthquakes;
they are not commonly felt by people and are generally recorded only on
local seismographs. Events with magnitudes of about 4.5 or greater - there
are several thousand such shocks annually - are strong enough to be recorded
by sensitive seismographs all over the world. Great earthquakes, such as
the 1964 Good Friday earthquake in Alaska, have magnitudes of 8.0 or higher.
On the average, one earthquake of such size occurs somewhere in the world
each year. Although the Richter Scale has no upper limit, the largest known
shocks have had magnitudes in the 8.8 to 8.9 range. Recently, another scale
called the moment magnitude scale has been devised for more precise study
of great earthquakes. The Richter Scale is not used to express damage.
An earthquake in a densely populated area which results in many deaths
and considerable damage may have the same magnitude as a shock in a remote
area that does nothing more than frighten the wildlife. Large-magnitude
earthquakes that occur beneath the oceans may not even be felt by humans.

Souce: This Information was provided by USGS - National Earthquake Information Center

Notes: It is possible that there is really only one
quake in 1268. Turkish sources do not list the event near Adana. Also, NG(2) seems to have very large casualty figures that are not included with Turkish sources. Therefore, a question mark has been added after the values.